TestYourVocab functions by means of a quick three-part test: the first part with a handful of words to determine the general vocabulary level, a second part with a larger but narrower selection of words to determine the vocabulary level with greater precision, and a final (optional) survey to collect statistical information.
TestYourVocab provides accurate results for virtually everyone, from very small children (with answers input by parents) to professional linguists. It can calculate vocabulary sizes from less than 100 words to more than 40,000 words.